#!/usr/bin/env python
# -*- test-case-name: twisted.names.test.test_examples -*-

# Copyright (c) Twisted Matrix Laboratories.
# See LICENSE for details.

"""
Print the SRV records for a given DOMAINNAME eg

 python dns-service.py xmpp-client tcp gmail.com

SERVICE: the symbolic name of the desired service.

PROTO: the transport protocol of the desired service; this is usually
       either TCP or UDP.

DOMAINNAME: the domain name for which this record is valid.
"""

import sys

from twisted.internet.task import react
from twisted.names import client, error
from twisted.python import usage


class Options(usage.Options):
    synopsis = "Usage: dns-service.py SERVICE PROTO DOMAINNAME"

    def parseArgs(self, service, proto, domainname):
        self["service"] = service
        self["proto"] = proto
        self["domainname"] = domainname


def printResult(records, domainname):
    """
    Print the SRV records for the domainname or an error message if no
    SRV records were found.
    """
    answers, authority, additional = records
    if answers:
        sys.stdout.write(
            domainname + " IN \n " + "\n ".join(str(x.payload) for x in answers) + "\n"
        )
    else:
        sys.stderr.write(f"ERROR: No SRV records found for name {domainname!r}\n")


def printError(failure, domainname):
    """
    Print a friendly error message if the domainname could not be
    resolved.
    """
    failure.trap(error.DNSNameError)
    sys.stderr.write(f"ERROR: domain name not found {domainname!r}\n")


def main(reactor, *argv):
    options = Options()
    try:
        options.parseOptions(argv)
    except usage.UsageError as errortext:
        sys.stderr.write(str(options) + "\n")
        sys.stderr.write(f"ERROR: {errortext}\n")
        raise SystemExit(1)

    resolver = client.Resolver("/etc/resolv.conf")
    domainname = "_%(service)s._%(proto)s.%(domainname)s" % options
    d = resolver.lookupService(domainname)
    d.addCallback(printResult, domainname)
    d.addErrback(printError, domainname)
    return d


if __name__ == "__main__":
    react(main, sys.argv[1:])
